Embodiments described herein relate generally to ventilation of a combustion engine. More specifically, embodiments described herein relate to ventilation of blow-by gas from a crankcase of a combustion engine.
During operation of a combustion engine, gas is pressed out of the combustion chamber and into a crankcase through a gap between a piston ring and a cylinder wall. The gas that is pressed out through the gap is called blow-by gas. Unless removed from the crankcase, the blow-by gas increases the pressure inside the crankcase.
Conventionally, the blow-by gas may be vented from the crankcase to the ambient, however blow-by ventilation to the ambient is considered part of a vehicle's total emissions. For this reason, emission of the blow-by to the ambient is usually avoided.
The blow-by gas may also be vented to an engine intake, for example via a crankcase vacuum pressure regulating valve. Venting blow-by gas to the engine intake can potentially contaminate the air intake hardware, such as the compressor or the intake manifold. Additionally, particulates can form when the blow-by gas is combusted in the combustion chamber.
Another method of venting the blow-by gas is forcing the blow-by gas into the exhaust gas so that both emissions are treated by an aftertreatment system of the vehicle, for example either a diesel oxidation catalyst (DOC) and/or a diesel particulate filter (DPF). To inject the blow-by gas into the exhaust, the blow-by gas must be heated and compressed so that the blow-by gas can remain in a gas phase. Additionally, oil mist in the blow-by gas may deposit on the DOC and cover the active sites of the catalyst, which may lower the effectiveness of the aftertreatment system, for example by lowering levels of passive DPF regeneration and increasing the light-off temperatures needed for active DPF regeneration. Alternatively, the blow-by gas emissions may result in higher rates of ash accumulation at the DPF, which may require more frequent ash removal servicing.